In all present drilling operations to date in offshore drilling with a semi submersible rig or drillship, this top hole drilling is performed riserless. The debris and drill cuttings are until now handled in two different ways. 1) The returns are discharged and flow freely into seawater as the drilling fluid and formation debris are pumped up the hole. The drilling fluid and formation will then be spread out on the seabed around the borehole. 2) After the well is spudded and the first structural/conductor casing is set, some equipment is run on the drill string that will connect to a suction hose and a pump placed on seabed. The majority of the drill fluid and cuttings is then sucked from the top of the hole and pumped away from the drill site to a different location on seabed. This cutting transport system will not remove the cuttings from the seabed but just re-locate them.
Lately concepts have been presented that will pump the return from seabed up to the drilling platform thorough a separate hose with the help of a pumping system on seabed after the structural or conductor casing has been set. This is indicated in patent NO312915. Here the pump is place on the seabed and no drilling riser is installed.